It has been conventional practice in forming glass fibers or filaments by attenuating streams of heat-softened glass flowing from a stream feeder or bushing having depending orifice projections through which streams of glass are flowed and are attenuated to continuous fibers or filaments by winding a strand or linear group of the fibers or filaments into a wound package. In the use of a stream feeder or bushing having rows of depending tips or projections provided with stream flow orifices, the projections have been spaced sufficiently to accommodate metal fin shields for conveying away heat from the glass streams to thereby render the glass in a more viscous condition for attenuation of the glass streams to fine fibers or filaments.
Endeavors have been made to increase the production of fibers by using an orifice plate or floor of a feeder or bushing having very short orificed projections or using a tipless plate or tipless bushing floor having orifices formed therein. As such orifice plate or bushing floor has considerably more stream flow orifices to attain increased production of fibers or filaments, the orifices are closely spaced so that there is insufficient space to accommodate metal fin shields.
There has been considerable activity in the glass fiber or filament-forming field to develop a process and apparatus for controlling the fiber-forming environment wherein the glass streams flow through closely spaced orifices in a flat plate or tipless bushing floor or an orifice plate or bushing having closely spaced, very short depending orificed projections.
Developments in this field include the use of a nozzle construction positioned below the orifice plate or bushing floor from which an upwardly directed flow of air impinges on the orifice plate or orificed bushing floor. The impingement of cooling air upwardly onto the orifice plate or bushing floor cools the molten glass flowing from the orifices to maintain fiber separation and to eliminate any stagnant air or gas at the under surface of the orifice plate or bushing floor.
Difficulties have been encountered in maintaining a stable glass fiber-forming environment utilizing gas or air flow from a nozzle construction. Difficulties can also arise in restarting fiber or filament-forming operations after there has been an interruption of attenuation or filament break-out in a process using a feeder having very short depending orifice projections or in the restarting of filament-forming operations utilizing a tipless orifice plate or bushing floor.
Restarting filament-forming operations from a tipless bushing is particularly difficult because a tipless bushing does not form beads of glass at the orifices as does an orifice plate or bushing floor having conventional depending projections. Restarting attenuating operations in the process require a highly skilled operator and restarting operations are time consuming.